1. Field of the Invention
The present invention relates generally to a rotary turbine fluid pump for pressurizing and circulating fluid. More specifically, the invention relates to a rotary turbine fluid pump suitable for use as a fuel pump for supplying a fuel to an automotive internal combustion engine.
2. Description of the Background Art
Conventionally, roller vane type fuel pumps have been used as a fuel pump for an internal combustion engine. In the recent days, non-volume type rotary turbine fuel pumps are inclined to be used in place of the conventionally used roller vane type fuel pumps.
The rotary turbine fuel pump has a turbine vane rotatingly driven by means of an electric motor. The turbine vane is disposed within a path of the fuel to pressurize the fuel introduced into the fuel path. A substantially small gap is formed between the inner periphery of the fuel path and the edge of the turbine vane. The gap is sealed by establishing floating seal. When leakage of fuel through the gap occurs, the performance can be necessarily lowered. Therefore, in order to maintain satisfactory performance, gap has to be small enough to successfully establish the floating seal.
In such rotary turbine fuel pump, problem is encountered when pressure balance in the floating seal is destroyed. Namely, when the pressure balance is destroyed, the turbine blade is depressed onto the inner periphery of the fuel path to substantially increase friction to cause lowering of the pump performance and wearing of the blade.